Jonathan Brown and Paul Maslin at Salonare wondering today whether pollsters are undercounting Barack Obama's support by millions of voters because they are failing to survey cellphone-only users, a growing portion of the population, especially the population of young adults most likely to have only cellphones and which showed a strong preference in the primaries and caucuses for the Illinois Senator. (Maslin was Howard Dean's pollster in 2004, and polled for Bill Richardson this year. Brown works for Fairbanks, Maslin, Maullin & Associates, a public opinion research firm.)

Say you want to reach a representative sample of the U.S. electorate for a presidential poll. The Obama-McCain race is relatively close these days, with the Democrat's lead hovering around 5 to 6 points in most surveys. Someone tells you that he's selected a sample that's predominantly under 40 years of age (oops, that one favors Obama); disproportionately renters rather than homeowners (Obama-leaning again); full of college students (sounds like a Starbucks Obama thing to me) - and, for good measure, includes a higher proportion of blacks and Hispanics than the national population does.

At this point you throw up your hands and exclaim: "Why are we concentrating on such a pro-Obama universe? He could be leading by 20 points or more among those people!"

He could. He probably is. But in actuality, the sample I've described is either not being included at all in many national polls or is being undercounted. Why? Because I'm talking about the growing number of American cellphone users who have no other type of phone or who choose to go wireless for the vast majority of their interactive needs. And this election cycle -- for the first, and perhaps only, time -- this group has the chance to render presidential polls "wrong from the start": potentially disguising at least 2 to 3 percentage points of Obama support and maybe more. Heretofore my industry has dismissed the cellphone-only population with a troika of "yes, buts." Yes, they're undercounted, but 1) they don't vote anyway; 2) their numbers are still small; and 3) we can find acceptable substitutes in the land-line population.

And to be honest, there is a fourth, still more powerful rationale that remains unstated: "Yes, they're undercounted, but it's too damn difficult and expensive to reach them."

In 2004, the National Election Pool exit poll found that 7.1 percent of voters were cellphone-only users, a figure the authors think could be twice as high this year.

Pollsters, Brown and Maslin write, don't like to survey cellphone-only users because, by law, they can't automatically dial them, and manually dialing them costs more and takes more time. Moreover, these users tend to be less cooperative. But taking the easy way out could prove problematic.

This year, the increasingly inexcusable failure to count a growing pool of voters could prove mathematically embarrassing. Let's say that with the campaigns' increased focus on the Web, Facebook, phone-texting and other targeted ways to communicate to younger Americans, voter turnout rises and this cellphone-only universe climbs from under 10 percent of the electorate to something closer to 20 percent. If these voters' preference is 60-40 for Obama, they alone will increase his national total by 2 percentage points. And those could easily be conservative projections. In fact, Gallup Poll results from earlier this year (prior to Obama's designation as the presumptive Democratic nominee) had a 4-point swing in favor of Obama once cellphone-only respondents were folded into the overall sample.

If Maslin and Brown are right, pollsters who continue to take the easy path this election year could wake up red-faced on the morning of November 5.